1. Field of the Invention
The present invention relates to a battery adapted to be located in a battery encapsulation, of the type having first and second encapsulation parts joined by a weld along a weld zone.
The invention also relates to such a battery encapsulation, and a battery unit having such a battery and such a battery encapsulation, the battery being located in the encapsulation.
The invention also relates to an implantable medical device that has such a battery unit. Typically, the implantable medical device is a heart stimulating apparatus.
It should be noted that the invention particularly relates to a battery unit, a battery and a battery encapsulation wherein the first and second encapsulation parts are joined by welding with the battery being disposed in the encapsulation, generally in its operative position in the encapsulation.
2. Description of the Prior Art
Since the invention is particularly applicable to batteries and battery units of implantable medical devices such as heart stimulating apparatuses the background of the invention is described with reference to such an application.
Batteries for implantable medical apparatuses are encapsulated in encapsulations made of a material compatible with the human body. Such materials are metals such as stainless steel or titanium.
The encapsulation is constituted of two or more parts that have to be joined with the battery positioned inside the encapsulation. Preferably the encapsulation parts are joined by means of welding along overlapping edges thereof.
Welding will result in heat being generated in the very vicinity of the battery itself. Normally, the battery is covered with an electrically insulating material, for example a polymer. The heat might negatively affect the battery or the insulating material covering it since the battery is located close to the weld during the welding.
The conventional way to solve this problem is to use a support element, usually a polymer structure, which separates the battery from the encapsulation in the weld region. The support element may have a recess opposite the weld, thereby providing a clearance between itself and the weld zone or weld region. The support element thus prevents heat transfer through conduction directly to the support element, and the battery. However, some space that could otherwise have been used as battery space is lost in the encapsulation due to the presence of the support element. The support element also adds cost to the battery unit.